Structural Insights into the Polymorphism of Self-Assembled Amylin Oligomers

Type 2 diabetes (T2D) affects over 300 million people worldwide. The main component, found in the pancreas of 95 % of T2D patients, is amylin oligomers and fibrils. So far, four different molecular structures of the self-assembled amylin oligomers have been observed experimentally: two ssNMR models and two crystal models. This review illustrates that there are further self-assembled amylin oligomers that differ in the orientations of the side chains along the β-arch and are all derived from the two ssNMR models. This review focuses on polymorphism of the self-assembled amylin oligomers. It also provides the various pathway mechanisms which lead to various amylin oligomers. Finally, it illustrates that interactions of amylin oligomers with further amyloids, such as Aβ oligomers, increase the polymorphism by forming polymorphic states of amylin-Aβ oligomers with various pathway mechanisms. The polymorphism of amylin oligomers and the polymorphism of the cross-seeding amylin-Aβ oligomers phenomena could contribute to explaining, at least in part, the still unknown origins of the pathological conditions, and may assist in preventing aggregation in amyloidogenic diseases with drug design and other therapeutic approaches.